Okay, I have had this for probably 30 years and have shown it to numerous people with no one having a clue as to what it is.
It looks like milk glass, the stem is about 5 inches long and has a round cap on one end that screws off. The only marking is an arrow and the word "Top" on the fixed end of the stem , see last photo.
I thought something to do with bottles or cookware but no ideas of purpose.
Any help would be appreciated even if it's a wild guess.